"Sharp, quirky, and occasionally nettlesome", Walking the Berkshires is my personal blog, an eclectic weaving of human narrative, natural history, and other personal passions with the Berkshire and Litchfield Hills as both its backdrop and point of departure. I am interested in how land and people, past and present manifest in the broader landscape and social fabric of our communities. The opinions I express here are mine alone. Never had ads, never will.

May 11, 2006

Extinction by the Numbers

Scientists estimate that there are more than 30 million species of organisms - plants, animals, bacteria, fungi and protists- alive on planet Earth today. About half of these are rain forest species, and most of them are found in the forest canopy. These forests are disappearing at the astonishing rate of 100 acres each minute worldwide, or 52,560,000 acres every year.

E.O. Wilson in Biodiverisy (1988) and The Diversity of Life(1992) estimates that the background rate of extinction in all this diversity should be 1-3 species a year. Scientists differ, but estimates say we are experiencing between 1,000 and 10,000 times greater rates of extinction today and that these rates are both unprecedented and increasing. According to Wilson, in the 1970s, the extinction rate was about one species a day, or at least a hundred-fold increase above the base rate. A decade later it was one species every hour, or 8,760 species gone extinct each year. The current rate of extinction is far higher, with estimates that 100 species a day, or 365,000 each year, could go extinct in the first decades of the 21st Century.

On the other hand, for long-lived organisms it requires tens of thousands of years for speciation to occur and new species to emerge. The Asiatic brown bear and the American grizzly are subspecies of the same animal, separated since the end of the last glacial period but still capable of interbreeding. There are some fertile hybrids out there, such as Ogden's Pondweed (Potomogeton ogdenii), which since it was first described by science a few decades ago is known from only a handful of freshwater systems in western New England and Eastern New York. Conceivably, this globally rare organism could go extinct and then reappear if both its parent plants remained viable and promiscuous. There are not many species with that luxury. Richard Leakey offered the opinion at a lecture I attended several years ago that Homo sapiens sapiens has stopped evolving.

The argument that extinction and recovery are part of the earth's natural cycle disregards the pace and global nature of the current extinction event, our role in accelerating it, and the amount of recovery time the planet will need to diversify once again. Even the great extinction event at the end of the Mesozoic Era that closed the age of the non-avian dinosaurs affected fewer species and some portions of the globe more heavily than others.

Humans are capable of responding to what we perceive and changing behaviors both as individuals and collectively. How many of us can perceive the extinction of hundreds of thousands of species every year when we have direct experience with few, if any of them? Drowning walruses and starving polar bears are charismatic fauna impacted by climate change in highly visible and dramatic ways. Who sees the rainforest canopy, one of the last terrestrial frontiers and until recently virtually inaccessible to science? How are we to turn these numbers into meaningful experience while there is still time to mitigate our role in this period of extinction?

Today is by Senate declaration Endangered Species Day. Tip of the Hat to Lene at Whorled Leaves for the serendipitous posting.